Conventionally, rubber sheets used as carcasses and belts of tires have a plurality of cords extending in their length direction embedded therein. These rubber sheets are fabricated by covering both surfaces of the cords with rubber extruded from calender rolls while a plurality of parallelly arranged cords are being conveyed. In the process of covering the cord surfaces with rubber, excess pieces are formed on both width end sides of the rubber sheet. Thus protrusion rubber as the protrusion portion of the sheet is formed by cutting off the excess pieces at appropriate positions.
As a method of forming protrusion rubbers which are the protrusion portions, a rubber sheet cutting apparatus as described in Patent Document 1 has been proposed.
With the above-mentioned apparatus, however, since it actually measures the width of the rubber sheet with its width sensor and estimates the width of protrusion rubber based on the measured width of the rubber sheet, there may be cases where there occurs variation in positions of cords embedded in the rubber sheet without any change in the width of the rubber sheet during fabrication. And this can cause deviations in the positions of the embedded cords along the width direction of the rubber sheet. In such cases, protrusion rubbers of a predetermined length cannot be formed by cutting off the excess pieces with accurate dimensions, and furthermore the body part of the rubber sheet where cords are embedded can be cut into accidentally.